# AC Circuit/power factor

Discussion in 'Homework Help' started by ladysman217, Mar 31, 2008.

Mar 31, 2008
7
0
Hi,
Im new to this site so dont know exactly how it works. However i would like to post a question cause i could use some help.

I have a ac circuit
R=7+0j ohm and L=0+10j Vsource =50<0 degrees

the question is: what value of capacitance should i have to bring the power factor to unity?

would you be able to tell me at least how to do it?
i have tried using the method on the sit but i still cant get it to work.

the answer i got when i did the question was 149.5 micro farads

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
calculate the impedance of the inductor and then calculate the value of the capacitor which gives the same impedance.

The resistor and the inductor are in series , i think, so put the capacitor in parallel with them.

3. ### silvrstring Active Member

Mar 27, 2008
159
0
You must know the frequency--or the inductance, so you can then find the frequency--to find the needed capacitor. I don't see either of these in your question.

Also, is R in parallel with L, or are they in series? The reactive power Q you are trying to balance will be different in series vs. parallel.